diff --git a/test/integration/proxy.test.ts b/test/integration/proxy.test.ts
index f254d57..4ee2dca 100644
--- a/test/integration/proxy.test.ts
+++ b/test/integration/proxy.test.ts
@@ -13,7 +13,9 @@ vi.hoisted(() => {
 });
 
 let downstream: ReturnType<typeof serve>;
-let captured: { auth?: string; fake?: string; path?: string; method?: string; body?: string } = {};
+let captured: {
+  auth?: string; fake?: string; path?: string; method?: string; body?: string; trace?: string;
+} = {};
 /** 主机保全见证：只有真打到"配置的下游"这台服务的请求才会记进来（C1 回归用） */
 const hits: string[] = [];
 
@@ -41,6 +43,7 @@ describe('gateway proxy', () => {
         path: c.req.path,
         method: c.req.method,
         body: await c.req.text(),
+        trace: c.req.header('traceparent') ?? '',
       };
       return c.json({ from: 'downstream' });
     });
@@ -114,6 +117,25 @@ describe('gateway proxy', () => {
     }
   });
 
+  // 网关是外部请求的第一跳：缺 traceparent 补发一条，已有的绝不覆盖。
+  // 两条断言互为反向：去掉注入那行 → 第一条红；把 `!` 去掉（无条件 set）→ 第二条红。
+  it('traceparent：缺则补发合法形状，已有则原样透传不覆盖', async () => {
+    captured = {};
+    const injected = await buildApp().request('/api/task/task/t-1/view', {
+      headers: { authorization: `Bearer ${token}` },
+    });
+    expect(injected.status).toBe(200);
+    expect(captured.trace).toMatch(/^00-[0-9a-f]{32}-[0-9a-f]{16}-01$/);
+
+    captured = {};
+    const mine = '00-0123456789abcdef0123456789abcdef-89abcdef01234567-01';
+    const passed = await buildApp().request('/api/task/task/t-1/view', {
+      headers: { authorization: `Bearer ${token}`, traceparent: mine },
+    });
+    expect(passed.status).toBe(200);
+    expect(captured.trace).toBe(mine);   // 覆盖＝把上游已开好的链从中间截断
+  });
+
   it('下游 gzip 响应：解码后的 body 不得再带 content-encoding（D9）', async () => {
     const res = await buildApp().request('/api/task/gzip', {
       headers: { authorization: `Bearer ${token}` },